The present invention pertains to a process for effective regeneration of used catalyst to remove deposited carbon and sulfur compounds by staged controlled burnoff. It pertains particularly to a continuous process in which the used carbon-coated catalyst is successively contacted by hot gas streams at increasing temperature levels and containing increasing O.sub.2 concentrations in multiple zones to effectively burn off the carbon and sulfur compounds.
Cataysts deactivated by carbon deposition in hydroconversion processes can be regenerated by in-situ carbon burnoff in a controlled oxidative atmosphere in fixed bed, or fluidized bed apparatus. For example, U.S. Pat. No. 4,007,131 to Gillespie, et al shows a process for regenerating catalyst from hydroprocessing operations in a reactor by passing hot inert gas containing 0.1-4.0 V % oxygen through the catalyst while in-situ in the reactor. However, such in situ catalyst regeneration requires shutdown of the reaction process for the time needed to perform the regeneration, which may require many hours. Also, some channelling of the hot gas flow in the catalyst bed usually occurs and results in undesired variations in the degree of catalyst regeneration achieved. Thus, more effective external catalyst regeneration procedures not requiring process shutdown have been sought. However, available external type commercial catalyst regeneration processes have not used apparatus which can maintain good control of gas temperatures and oxidative atmospheres. Consequently, the quality of catalyst regeneration from external type systems is not entirely satisfactory. Catalysts regenerated by these processes have only moderate recovery of pore volume and surface area and have high content of sulfate sulfur, which is a poison for the catalyst. Also, the existing catalyst regeneration processes are costly because of the huge apparatus used for the carbon burnoff.